<body bgcolor="orange">
    <canvas width="300" height="300" id="testcase-canvas-dest"></canvas>
  <script>
    const kTransparent = "rgba(0%, 100%, 100%, 0.5)";

    cx2 = document.getElementById('testcase-canvas-dest').getContext('2d');
    cx2.fillStyle = kTransparent;
    cx2.fillRect(0,0,100,20);
  </script>

</window>
